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Science 22 July 2005:
Vol. 309. no. 5734, p. 532
DOI: 10.1126/science.309.5734.532p
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The protein component of chromatin, which consists of nucleosome octamers for the most part, is much more than a passive packing material--it plays an active role in controlling both the accessibility and activity of the DNA it sequesters. Yuan et al. (p. 626, published online 16 June 2005; see the 17 June News story by Marx) present a genome-wide analysis of chromatin structure at the level of individual nucleosomes, using tiled microarrays to determine the positions of nucleosomes along the length of an entire yeast chromosome, as well as many additional regulatory regions. The majority of nucleosome positions are remarkably well preserved, especially over genes, except for those undergoing high levels of transcription. Furthermore, functional transcription binding sites and yeast promoters are mainly nucleosome-free. These nucleosome-free intergenic regions are highly conserved among yeast species, and enriched in poly(dA-dT), hinting at a causal role in nucleosome positioning.




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Science. ISSN 0036-8075 (print), 1095-9203 (online)